1. Field of the Invention
The present invention relates to a display apparatus and more particularly to an addressable matrix of field effect picture elements utilizing the selective diode switching of voltages for picture element turn-on and charge-retention in each of two modes of operation.
2. Description of the Prior Art
In the prior art, many types of display circuits utilizing diodes have been proposed.
U.S. Pat. No. 3,532,813 discloses a display circuit which includes a matrix of display means. Each display means includes a dynamic scattering nematic liquid crystal cell and a capacitor connected in shunt with the cell through the relatively low impedance of a fast reset pulse generator for the row containing the cell. The addressing means for each display means includes a first diode to charge the cell in the associated display means and a second diode to erase the cell in that display means. A row pulse generator is connected to each row of the matrix and a column pulse generator is connected to each column of the matrix. In addition, a reset pulse generator is connected to each row of the matrix. Selection of a liquid crystal cell to light up is accomplished by the coincidence of the row and column pulses for that cell. This enables current to flow through the first diode to cause both dynamic scattering to occur in the liquid crystal cell and the shunt capacitor to become charged. After the coincident row and column pulses for the cell have terminated, the shunt capacitor discharges into the liquid crystal cell, maintaining it in its dynamic scattering condition. Immediately prior to the time that it is desired again to write information into a liquid crystal cell, the reset pulse generator for the row containing that cell is turned on. When turned on, the reset pulse generator applies a negative pulse to each of the second diodes in that row to cause the shunt capacitors and internal capacitances of the cells in that row to discharge through those diodes. After the negative pulse produced by the reset pulse generator terminates, but before the next row and column pulses, the fast reset pulse generator for the row containing the cell applies a pulse across the shunt capacitors and cells in that row to turn off the cells in that row.
U.S Pat. No. 4,065,764 discloses a liquid crystal display device which comprises mutually insulated numeric segment electrodes for forming numeric characters, mutually insulated digit segment electrodes opposed to the numeric segment electrodes, liquid crystal interposed between the numeric segment electrodes and the digit segment electrodes, switching elements such as diodes selectively coupled to the digit segment electrodes and a driving circuit operable in accordance with digit signals and numeric signals to drive the segments in the liquid crystal display device in a time division multiplex manner. The diodes connected to the digit segment electrodes operate to prevent undesired crosstalk between the segments as the liquid crystal display device is driven.
U.S. Pat. No. 4,297,695 discloses an electrochromic display device comprised of a matrix of column lines and row lines. The matrix is divided into submatrices, each submatrix being defined by a pair of column lines which intersect with a pair of row lines to form four points at the four intersections in the submatrix. Each individual point in the matrix is addressable to produce a local color change in the electrochromic material of the device by sequentially applying expose and develop pulses to that point. To build up an image of graphic information in the display device, short expose pulses are applied via diodes to associated pairs of column and row lines to only those submatrices in which a particular point is to be addressed, and then longer develop pulses are applied via diodes to individual columns and individual rows to the point in each of the exposed submatrices. This procedure is repeated for each of the remaining points in the selected submatrices, thereby covering all of the other desired corresponding points in the submatrices to complete the image. For a matrix comprised of a set of 5 by 7 submatrices, this procedure would be performed 35 times.